This application is claims priority of French application no. 01 15300 which was filed on Nov. 27, 2001, and was not published in English.
The invention concerns a device for indicating incorrect closure of locking means, consisting of a plurality of locking mechanisms located between two fan cowlings of an aircraft engine nacelle.
Such a device may in particular be used to immediately indicate incorrect closure of these cowlings to ground personnel.
The engine nacelles are typically equipped with cowlings, which can be opened, on the ground, to provide access to various items of equipment, systems, etc., for maintenance purposes. When the aircraft is in flight, the cowlings are closed and are shaped such as to provide aerodynamic continuity for the engine as a whole.
More specifically, the nacelles for twin-spool turbofan engines are equipped with at least a pair of fan cowlings, respectively on the right hand and left hand sides, surrounding the fan of the engine. Each of these cowlings exhibits a cross-section which is approximately C-shaped as viewed on a transverse plane perpendicular to the engine longitudinal axis. A hinge is provided along the top edge of each cowling to enable it to articulate from the top of the engine. Due to this arrangement, it is possible to gain access to the various equipment items of the engine, in particular for maintenance purposes, by raising the cowlings.
Additionally, the bottom edges of the cowlings are equipped with locking mechanisms for securing together the cowlings in their closed position when these mechanisms are locked. These locking mechanisms generally include a male part and a female part, mounted on the respective bottom edges of the cowlings, such as to be able to mate when the cowlings are closed.
In flight, several factors generate centrifugal forces acting on the cowlings. For example, the aerodynamic flow over the cowlings, possible overpressure caused by burst pipes inside the engine, or the presence of ventilation devices can be cited.
In consequence, the locking mechanisms are intended to withstand such forces in order to maintain the fan cowlings secured to the engine. For safety reasons, the number of mechanisms fitted is generally greater than the number required to withstand the loads generated by such centrifugal forces.
U.S. Pat. No. 4,531,769 concerns an advanced locking mechanism for securing together the two cowlings surrounding an aircraft engine. This mechanism, of the hook latch type, includes a main hook articulated from the bottom edge of a first cowling, in order to penetrate inside the corresponding opening provided on the other cowling. The position of the main hook is secured by the use of a second hook. The mechanism is locked by pushing on a handle.
When such a locking mechanism is installed on an aircraft engine, it is possible for the operator responsible for closing the cowlings, to omit to lock the mechanism, or to lock it incorrectly. In fact, when a locking mechanism such as that described in U.S. Pat. No. 4,531,769 is used, it is possible to actuate the handle in the direction for closure whilst the hook is not engaged in the corresponding opening provided on the other cowling. In such case, as in the case when the operator omits to actuate the locking mechanism after lowering the cowlings, it is nearly impossible to see that the locking has been omitted or incorrectly performed. In fact, due to their considerable weight, the cowlings automatically position themselves by gravity and their bottom edges hardly extend below the air intake. Moreover, the existing locking mechanisms do not incorporate any truly protruding parts which could indicate incorrect closure to the operator.
In European Patent application No0,596,070, this problem has been resolved by installing on the bottom edge of one of the two cowlings, a pivoting or sliding arm which hangs down visibly under the engine when the two cowlings are lowered but not secured. The incorrect closure indication can be further improved by adding a flag to the end of the pivoting or sliding arm.
According to this document, the securing of the cowlings can only be achieved after the operator has manually raised the arm and stowed it in a receptacle provided for the purpose. When the locking is performed, a pin mounted on the opposite cowling penetrates into the arm to secure it in the retracted position. When the cowlings are unlocked, a spring automatically deploys the arm in the protruding position, which is visible from outside.
However, this indicator does present a certain number of disadvantages.
First of all, in the most frequent case, where the engine is mounted beneath the aircraft wing, the cowling locking mechanism is located beneath the engine, in a position very close to the ground and therefore awkward to access. When the operator opens or closes the cowlings, he must squat down in order to operate the locking mechanisms. The arm added to the locking mechanism then constitutes a protrusion in addition to the blunt parts of the engine which may injure the operator.
Additionally, when closing the cowlings, the indicator described in European Patent application No0,596,070 involves the operator raising an arm whilst securing together the cowlings. In the position in which he finds himself, this operation can be particularly fastidious and difficult to perform.
Moreover, the indicator described in this document significantly complicates the existing locking mechanisms, since it requires alignment between the pin which locks the arm in the retracted position and the hole provided in the arm to accommodate this pin. This operation may be fastidious, in view of the wear and tear to which the parts are subjected in use.
Also, the indicator described in this document is not able to indicate an incorrect closure of all of the mechanisms involved for securing together the engine cowlings.
Indeed, the indicator is liable to move from its retracted position to its protruding position, only if none of the locking mechanisms are engaged.
In flight, however, in order to ensure the cowlings are secured together, it is habitually necessary to provide a plurality of locking mechanisms, in order to avoid any possibility of the engine cowlings being torn off.
However, in the document presented above, when only one of the locking mechanisms is engaged, it is sufficient to prevent the device from indicating incorrect closure, without any attention being drawn to the state of all the other mechanisms. This is particularly worrying in that it is possible for this to lead to situations where the ground personnel are not made aware of inadequate locking to secure the cowlings in flight.
European Patent application No1,099,629 describes an incorrect closure indicator for locking means which includes retractable stop means which automatically hold the two cowlings apart, when the cowlings are moved from the open position to the closed position.
Although this addresses the main disadvantages of the device described in European Patent application No0,596,070, this indicator does introduce a similar disadvantage to one of those associated with European Patent application No0,596,070.
The disadvantage is that associated with the inability of the indicator to detect incorrect closure occurring on any mechanism of the locking means. Indeed, once the indicator has been manually operated to allow closure of the locking means, the indicator is no longer able to provide any indication of the state of the various locking mechanisms.
Finally, in European Patent application No1,099,629, the indicator does not provide a sufficiently visible gap betwean the cowlings for the ground personnel to be able to detect incorrect closure of these cowlings. In consequence, the aircraft may take-off without the engine cowlings being correctly closed and secured together.
The invention is therefore intended to present a device for indicating incorrect closure of locking means consisting of a plurality of locking mechanisms located between two fan cowlings of an aircraft engine nacelle, this indicating device at least partially addresses the disadvantages described above with respect to indicators in accordance with the previous state of the art.
More precisely, the present invention is intended to propose an indicator device which provides a more reliable and better warning than that provided by the indicators in accordance with the previous state of the art.
To do this, the invention provides a device for indicating incorrect closure of locking means consisting of a plurality of locking mechanisms located between two fan cowlings of an aircraft engine nacelle, the device includes a body able to adopt, relative to the cowlings, a retracted position as well as a protruding position providing a warning of incorrect closure. According to the invention, the body of the device is able to cover at least partially at least two locking mechanisms when it is in its retracted position, the retracted position being exclusively authorised when each locking mechanism is able to be at least partially covered by the body of the device is locked.
Advantageously, when the two fan cowlings are spread apart, incorrect closure is indicated visually by the body of the indicator device. Moreover, the indicator device in accordance with the invention is designed such that if any of the locking mechanisms with which it is directly associated is incorrectly locked, the body of the device indicating incorrect closure cannot adopt the retracted position, and consequently obliges the operator to correctly lock each of the associated locking mechanisms that are unlocked. Therefore, as long as every locking mechanism associated with the indicator device is not properly locked, the body of the device cannot be folded to the retracted position in which it covers at least partially each of the associated mechanisms, and remains in a protruding position warning of incorrect closure.
Advantageously, although the body of the indicator device may be located underneath an aircraft engine, as described in European Patent application No0,596,070, its shape and its dimensions may be adapted to make it easily visible by an operator performing various tasks in the vicinity of the engine.
Preferentially, each of the locking mechanisms not locked and able to be at least partially covered by the body of the device constitutes a stop for the body, when moving it from its protruding position to its retracted position.
Preferentially, in its retracted position, the body of the device covers at least partially each one of the locking mechanisms which constitute the locking means, and is in contact with at least one of the two cowlings. In this way, by associating all the locking mechanisms to the indicator device, this device is capable of indicating incorrect closure if any one of the mechanisms constituting the locking means is incorrectly locked, thus enhancing the safety level provided by such a device.
According to a preferred embodiment of the invention, the body of the device is mounted freely articulated at one end of one of the two fan cowlings. Moreover, this indicator device includes closing means able to secure the body of the device to the other of the two fan cowlings.
The body of the device may therefore include a first part intended to cover each of the locking mechanisms when the body of the device is in its retracted position, and a second part intended to warn of incorrect closure when the body of the device is in its protruding position. Of course, if the indicator device is not associated with all the locking mechanisms constituting the locking means, but only with a certain number of them greater than or equal to two, the first part of the body of the device is then intended to cover only those concerned locking mechanisms.
According to another preferred enbodiment of the invention, the body of the device is mounted freely articulated from a part external to the two fan cowlings. Moreover, the device includes closing means able to secure the body of the device to at least one of these two fan cowlings.
In such case, the body of the device is intended on the one hand to cover each one of the locking mechanisms when the body of the device is in its retracted position, and on the other hand to warn of incorrect closure when the body of the device is in its protruding position.
Finally, the body of the device is apt to cover a predetermined number greater than or equal to two locking mechanisms, this number being adequate to withstand the loads generated by the aerodynamic flow encountered in flight. Thus the indicator device may be advantageously applied to a predetermined and limited number of locking mechanisms, according to the pertaining safety requirements.
Other advantages and characteristics of the invention will become evident from the following detailed description of the drawings when read in connection with the accompanying drawings which illustrate preferred embodiments of the invention.